Buckling of Rubber Bearings for Seismic Isolated Structures

The characteristics of rubber bearings used for seismic isolated structures involve the many unknown factors such as a mechanism at an ultimate stage. In case of design of themselves, experimental results are commonly used. For example, the results of regression analysis of test data are utilized for the design of buckling point, surface pressure, temperature and strain dependence for shear stiffness. Especially for buckling behavior, it is very important to estimate the precise point for more safety. In this paper, a prediction method of buckling point is proposed by considering the relationship between the stress of interlayer steel plate and shear strain of interlayer rubber. In this prediction method, it is considered that the buckling of rubber bearings is caused by the yield of steel plate around the center hole. To verify the method, finite element analysis (FEA) is carried out for whole the rubber bearing for several cases. From the results of FEA, it is also recognized that the yield of steel plate around center hole causes the buckling of rubber bearing. It is also confirmed that the buckling point predicted by proposed method show a good agreement with the load decreasing point of previous experimental results.